The present invention relates to offshore floating structures for installation and use in offshore operations.
Offshore floating structures (generally referred to herein as “platforms”), such as tension leg platforms (TLP), semi-submersible platforms, radar stations, offshore wind farms and the like may be anchored to the seabed and held in place in the ocean by means of mooring systems, such as tendons, steel catenary risers or similar mooring structures, which are typically fabricated from high strength, high quality steel tubulars, and include articulated connections on the top and bottom for connection to the floating structure and seabed anchor, respectively, that reduce bending moments and stresses in the tendon system. Many factors must be taken into account in designing an offshore floating platform to safely transport it to the installation site and keep it safely in place including: (a) limitation of stresses developed in the mooring system during extreme storm events and while the platform is operating in damaged conditions; (b) avoidance of any slackening of the mooring system and subsequent snap loading or disconnect of mooring system as wave troughs and crests pass the platform hull; (c) allowance for fatigue damage which occurs as a result of the stress cycles in the mooring system throughout its service life; (d) limit natural resonance (heave, pitch, roll) motions of the platform to ensure adequate functional support for personnel, equipment, and risers; (e) maximizing the hydrostatic stability of the platform during transport and installation; and (e) accommodating additional requirements allowing for fabrication, transportation, and installation.
These factors have been addressed in the prior art with varying degrees of success. Conventional multi-column offshore platforms, for example, generally have four vertical columns interconnected by pontoons supporting a deck on the upper ends of the vertical columns. Tendons connected at the lower ends of the columns anchor the platform to the seabed. In such conventional designs, the footprints of the deck, the vertical columns and the tendons are substantially the same and therefore hydrostatic stability of the platform can be a problem.
The present invention, in its various embodiments, addresses the above-described factors to accommodate different payload requirements, various water depths and to improve hydrostatic stability and hydrodynamic characteristics of the floating platform.